HLA-A*0201-restricted CD8(+) T-cell epitopes identified in dengue viruses

BACKGROUND: All four dengue virus (DV) serotypes (D1V, D2V, D3V and D4V) can cause a series of disorders, ranging from mild dengue fever (DF) to severe dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS). Previous studies have revealed that DV serotype-specific CD8(+) T cells are involved in controlling DV infection. Serotype cross-reactive CD8(+) T-cells may contribute to the immunopathogenesis of DHF/DSS. The aim of the study was to identify HLA-A*0201-binding peptides from four DV serotypes. We then examined their immunogenicity in vivo and cross-reactivity within heterologous peptides. METHODS: D1V-derived candidate CD8(+) T-cell epitopes were synthesized and evaluated for their affinity to the HLA-A*0201 molecule. Variant peptides representing heterologous D2V, D3V, D4V serotypes were synthesized. The immunogenicity of the high-affinity peptides were evaluated in HLA-A*0201 transgenic mice. RESULTS: Of the seven D1V-derived candidate epitopes [D1V-NS4a(56–64)(MLLALIAVL), D1V-C(46–54)(LVMAFMAFL), D1V-NS4b(562–570)(LLATSIFKL), D1V-NS2a(169–177)(AMVLSIVSL), D1V-NS4a(140–148)(GLLFMILTV), D1V-NS2a(144–152)(QLWAALLSL) and D1V-NS4b(183–191)(LLMRTTWAL)], three peptides [D1V-NS4a(140–148), D1V-NS2a(144–152) and D1V-NS4b(183–191)] had a high affinity for HLA-A*0201 molecules. Moreover, their variant peptides for D2V, D3V and D4V [D2V-NS4a(140–148)(AILTVVAAT), D3V-NS4a(140-148)(GILTLAAIV), D4V-NS4a(140-148)(TILTIIGLI), D2V-NS2a(144–152)(QLAVTIMAI), D3V-NS2a(144–152)(QLWTALVSL), D4V-NS2a(143–151)(QVGTLALSL), D2V-NS4b(182–190)(LMMRTTWAL)(,) D3V-NS4b(182–190) (LLMRTSWAL) and D4V-NS4b(179–187)(LLMRTTWAF)] also had a high affinity for HLA-A*0201 molecules. Furthermore, CD8(+) T cells directed to these twelve peptides were induced in HLA-A*0201 transgenic mice following immunization with these peptides. Additionally, cross-reactivity within four peptides (D1V-NS4b(183–191), D2V-NS4b(182–190,) D3V-NS4b(182–190) and D4V-NS4b(179–187)) was observed. CONCLUSIONS: Two novel serotype-specific HLA-A*0201-restricted CD8(+) T-cell epitopes (NS4a(140-148) and NS2a(144–152)) and one cross-reactive HLA-A*0201-restricted CD8(+) T-cell epitopes which is similar to a previously identified epitope were identified in D1V-D4V. Combining prediction algorithms and HLA transgenic mice is an effective strategy to identify HLA-restricted epitopes. Serotype-specific epitopes would be used to determine the protective role of serotype-specific CD8(+) T cells, while cross-reactive epitopes may provide assistance in exploring the role of serotype cross-reactive CD8(+) T cells in the immunopathogenesis of DHF/DSS.